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P2P Networks

This book is 60% completeLast updated on 2026-06-21
Jakob Jenkov

Peer-to-peer (P2P) networks are fascinating! P2P networks can scale to thousands, millions or even billions of individual peers collaborating without a central, coordinating entity. These peers can be run by individuals or organizations - each contributing resources towards the total capacity of the network. This book explores how!

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About

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About the Book

Peer-to-peer (P2P) networks are fascinating! P2P networks can scale to thousands, millions or even billions of individual peers collaborating without a central, coordinating entity. These peers can be run by individuals or organizations - each contributing resources towards the total capacity of the network. This book explores how!

P2P networks first became popular for file sharing use cases, but this is no longer the most popular use case. P2P networks have been used successfully for chat, voice and video calls in Skype at a global scale. P2P networks are also used in blockchain networks as well as in distributed hashtables (DHTs) and NoSQL databases. P2P networks are even being used by some media technology companies to distributed content at the edge, where their own hardware might be insufficient to serve local spikes in traffic.

Despite P2P technology actually being actively used in both consumer and enterprise software, P2P technology could be far more prevalent than it is today. Browsers could be supporting P2P communication. Application tech stacks could have built-in support for P2P topologies. Middleware products could be based on P2P technology. Modern media players could be accessing content via P2P networks.

There are probably multiple reasons why P2P technology is not as widely used as it could be. One reason probably is, that P2P techniques are not that well-described in the literature today. There are a few books available about P2P networks, but they tend to be either a bit superficial, or a bit academic in their writing style. This book is trying to alleviate that issue.

Another reason probably is, that the most popular P2P topology is the uniring topology used in Chord, Kademlia, Pastry and Tapestry. This uniring topology is not that well-suited for many use cases such as multicast, broadcast or geographically local communication. In this book I present the Polymorph polyring topology which seeks to address exactly these challenges.

Whatever the reasons are, changing the current state of affairs starts by applying our creativity and effort towards this goal. This book is intended as a first step on that path.

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Computers and ProgrammingNetworkingSoftware ArchitectureDistributed Systems

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About the Author

Jakob Jenkov

Jakob Jenkov is a technopreneur, software architect, veteran developer, Java Champion and writer / publisher focused on the big ideas in the software and tech industry. Jakob feels most at home in the nexus between business and technology.

Jakob pursues his interests via his company Jenkov Aps (jenkov.com). Jakob has published more than 800 technical articles which attact millions of readers every year, and produced a few videos which attract hundreds of thousands of viewers every year.

Jakob has worked with web development and enterprise software since 1998 - mostly consulting for larger companies. The later years Jakob has taken a step back from development to focus on software architecture an the business context in which it exists. Jakob prefers a scientific approach to problem solving, favouring deep analysis and evidence over shallow understanding, assumptions and opinions whenever possible.

Contents

Table of Contents

Thank You !

  1. Acknowledgments
  2. Social Channels

About This Book

Introduction to Peer-to-peer Networks

  1. Peers
  2. P2P
  3. Self-organizing
  4. Collaborative Computing
  5. Autonomy
  6. Global Scale
  7. Use Cases Drive P2P Technologies
  8. The P2P Landscape Today
  9. The P2P Internet - The Unfulfilled Potential
  10. The Future Potential of P2P

A Brief History of P2P Technology

  1. Early File Sharing
  2. Gnutella - 2000
  3. Chord - 2001
  4. Pastry - 2001
  5. Kademlia - 2002
  6. Skype - 2003
  7. Tapestry - 2004
  8. Hamachi - 2004
  9. Joost - 2007
  10. Bitcoin - 2008
  11. Cassandra - 2008
  12. Space Monkey - 2011
  13. IPFS - 2015
  14. LBRY - 2015
  15. Polymorph Polyring P2P Topology - 2021
  16. Additional P2P Technologies

P2P Network Definition

  1. Pure P2P Networks
  2. Hybrid P2P Networks

P2P Network Topologies

  1. P2P Topology Categories
  2. Unstructured P2P Topologies
  3. Structured P2P Topologies
  4. Hybrid P2P Topologies

Starting a P2P Project

  1. Defer the P2P Network Implementation
  2. Start With a Star Topology
  3. Evolve Towards a Pure P2P Topology

Polymorph Polyring P2P Topology

  1. Polymorph Polyring P2P Topology Design Goals
  2. The Polyring Topology
  3. Polyring vs. Tree Topology
  4. The Center Ring
  5. Subrings
  6. Peer GUIDs
  7. Ring Leaders
  8. Subring Leaders
  9. Direct + Indirect Ring Communication
  10. Routing Between Peers
  11. Topology Shaping
  12. Side Rings
  13. Broadcast and Multicast

Uniring P2P Topologies

  1. Uniring Routing Tables
  2. Uniring Implementations

Chord

  1. The Chord Routing Table and Distance Function
  2. Peer Lookup
  3. GUID Assignment

Kademlia

  1. The Kademlia Routing Table and Distance Function

Distributed Hashtables (DHT)

  1. Distributed Hashtables vs. Local Hashtables
  2. Distributed Hashtable Buckets
  3. Distributed Hashtable Scaling Challenges
  4. Modulo Mapping
  5. Consistent Hashing
  6. Rendezvous Hashing
  7. Dynamic Hashing

Change Log

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